Subsequent Event (Details) shares in Thousands, $ in Thousands	1 Months Ended	6 Months Ended
	Jul. 31, 2016 USD ($) aircraft shares	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)
Subsequent Event [Line Items]
Purchase of property and equipment		$ 303,175	$ 308,163
Payments for Repurchase of Common Stock		$ 62,278	$ 79,415
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock Repurchased During Period, Shares | shares	269
Payments for Repurchase of Common Stock	$ 12,100
Airbus A319 [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Previously Leased Aircraft Purchased | aircraft	3
Purchase of property and equipment	$ 58,800